The short from Hell

[Cajonpassfan]

I spent the entire day today, my day off, (not counting countless frustrating hours over the course of a year) chasing down a short on one of my power districts that had made the central portion of my layout inoperable and the rest of the layout pretty much useless. I tracked every hard to get to connection under scenicked portions of the layout, pulled off scenery, disconnected and unsoldered many blocks, cut wires to narrow down the problem, took the Ohm meter around inch by inch, and finally found the culprit: a sloppy loose edge connector on one of the 100 or so Tortoises I have that bridged the Tortoise contacts, below
I should be thrilled I finally found the problem (and I guess I am) but I am so royally pissed at myself (and the manufacturer) for creating such a stupid simple but deadly malfunction.
I think I'll celebrate tomorrow; tonight I'm just tired...
Good night, Otto

[GaryHinshaw]

Reminds me of an incident I had on TBC a few years ago where I somehow managed to get a steady 12 V across my (then-DC) rails via a Tortoise.  I don't remember how it happened, but it was kind of spooky to see my locos tear off like a bat out of hell!

Model Railroading is Fun.

[Cajonpassfan]

Model railroading IS fun; it's the flipping' wiring is not 

So I can't believe I'm the only one with this problem. Is there a simple way to prevent the edge connectors from sliding laterally? Do I need to put nonconductive shims inside the connectors? Or do I just hardwire future installs like I used to before I "discovered" the edge connectors? If the Tortoise card were just a bit wider, this wouldn't be an issue.
These are the ones I'm using, see below...
Otto K.

[ednadolski]

On some of my connectors I've glued in a styrene shim to prevent misalignments.  The rest are a problem waiting to happen.

What it really means is that the connectors are the wrong spec for the Tortoise.  Does anyone know of the correct one?

Ed

Edit: makes me long for the day when we can have dead rail in N scale 

[lyled1117]

This has been a pet peeve for me that the board doesn't match the size of standard connectors. The usual fix is to glue a piece of strip styrene into the connector on each side to keep it centered on the tortoise's edge connector. I have heard that somebody has created a connector that matches the size, if I can find it I'll post it

Lyle

[Chris333]

I've never used these, but swore I've seen the styrene shim trick in an article before.

[eric220]

I had a very similar experience last week. Turn on the layout and "click--click--click--click". After about half an hour, I traced it to.... A Tortoise! One strand of a stranded wire had come lose and wandered over to make contact with its neighbor.

[jdcolombo]

Easiest solution: don't use edge connectors (they are really a kludge, not specifically designed for the Tortoise's circuit board).  My Tortoises are wired with 5 wires (M+, M-, Track+, Track-, Frog out).  Before I install them, I solder five 18" lengths of color-coded wire to the appropriate terminals (red and black for track power; yellow and blue for motor; green for frog out).  Once the Tortoise is in place, I complete the wiring by using half of a 12-position European-style terminal block (Digikey, $2.20 in lots of 10, so $1.10 for each Tortoise).  The wires from the Tortoise go in the top of the terminal block, the supply wires in the bottom.  Easy to disconnect if I need to replace the Tortoise, and easy to disconnect individual wires for troubleshooting if necessary.  Never, ever had a wiring problem this way.

John C.

[Cajonpassfan]

John, NOW you tell me
This sounds like a great way to go, before one installs a hundred of them
Otto

[jdcolombo]

John, NOW you tell me
This sounds like a great way to go, before one installs a hundred of them
Otto

Well, heck, I thought everyone did it this way 

John

[C855B]

This has been a pet peeve for me that the board doesn't match the size of standard connectors. ...

Oooo, that's disappointing. I haven't used Tortoises so can't speak directly... but a connector mismatch like this is a basic design error. It easily could be they designed the board/edge connector around a specific brand and type of connector that was discontinued, or after tooling the board, changed connector source. However, it seems odd to me as a former designer of such things that there would be that much difference between 0.1"-pitch edge connectors. This connector type has been around for over half a century, and with that I tend to think that the specs are pretty cut-and-dried.

Then again, as John inferred they were not designed for edge connectors, it was just "lucky" that the wire solder pads were on 0.1" centers and could be used with modified (the styrene shim) edge connectors. As are all things hobby related, it's an issue of cost sensitivity - including the connector with the device would increase the end-user cost by about $1.50... or more, considering that solder-tab edge connectors are an electronics-design dinosaur.

Aaaaaaaanywaaaay... as we incorporate more and more electronics into our MRRs, folks are going to discover one of the truisms from my too-long career in electronic devices: the #1 source of failures is connectors, and flakiness thereof.

[basementcalling]

OK, this doesn't reassure me about my upcoming under the layout adventures, DCC and otherwise, at all.   

[jdcolombo]

OK, this doesn't reassure me about my upcoming under the layout adventures, DCC and otherwise, at all.   

I've learned the hard way that using the European-style terminal blocks EVERYWHERE is the best insurance against wiring problems.  I use them for the Tortoises, but I also use them for feeder wiring and for wiring the main bus between isolated sections of the layout.  It's a bit of a pain, but I use a standard 12-position block for track feeder wiring, one block for red and one for black.  I connect the track power to the top, daisy-chaining 1" lengths of 20-gauge SOLID wire across all 12 positions and feeding from the far left or right as needed, and then use the bottom portion to connect individual feeders.  If I have a short, I can undo the feed wire in 5 seconds, disconnecting all the feeders.  If that fixes the short, then I reconnect the main feeder, and unhook all 12 feeder wires.  Then I hook them back up one-by-one until I find the short.

Here's a photo that shows both the Tortoise wiring and my feeder wiring (I'm not a neat freak, so be forewarned that there are wires everywhere):



The thick red and black wires are the bus wires connecting this isolated section of the layout.  Disconnecting one of these disconnects the entire layout section.  The individual Euro terminal blocks are wired together with the short 1" daisy-chained wires, and the feeders come off the bottom.

And . . . I always use only SOLID wire for layout wiring.  Stranded wire has its uses, but there are too many opportunities for a stray strand of wire to cause problems under a layout.  Even my 12-gauge bus wires are solid copper.  They are not exactly flexible . . . but they get the job done.

John C.

[Cajonpassfan]

OK, this doesn't reassure me about my upcoming under the layout adventures, DCC and otherwise, at all.   

Peter, you'll be fine, really
John's advice about using terminal blocks is actually very practical. Aside from the edge connector problem, every time I have an issue is where I was cutting corners. The terminals make troubleshooting much easier; I had to cut some wires. The other (obvious) suggestion I'd make is to get most of your wiring done before too much scenery goes in. Amazing how much easier it is when you can actually see it and get to it
Best, Otto K.

[peteski]

Here is an example of the way my friend hooked these up under his layout. He soldered color-coded wires to the tortoise connecter and used crimp terminals on the other end. Then they are attached to the terminal blocks.  This is a very reliable solution and it makes it easy to troubleshoot any problems (since each wire can be individually detached from the terminal block).

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I also think that the edge connector was an afterthought rather than a design feature. If it was a design feature then I think that the circuit board would have been made wider to better fir the connector.  But if you want to continue using the edge connectors then installing styrene strips to properly align it with the circuit board is a viable (and easy) workaround.